InGaAlN LIGHT-EMITTING DEVICE AND MANUFACTURING METHOD THEREOF

ABSTRACT

There is provided an InGaAlN light-emitting device and a manufacturing method thereof. The light emitting device includes a conductive substrate having a main surface and a back surface, a metal bonding layer formed on the main surface of the substrate, a light reflecting layer formed on the bonding layer, a semiconductor multilayer structure including at least a p-type and an n-type InGaAlN layer disposed on the reflecting layer, the p-type InGaAlN layer directly contacting the reflecting layer, and ohmic electrodes disposed on said n-type InGaAlN layer and on the back surface of the conductive substrate, respectively.

RELATED APPLICATION

This application is a national-stage application of and hereby claimspriority under 35 U.S.C. § 371 to the PCT Application No.PCT/CN2006/001100, filed 26 May 2006, which claims priority to ChinaPatent Application No. 200510026306.5, filed 27 May 2005.

TECHNOLOGY FIELD

The present invention relates to a type of indium gallium aluminumnitride (In_(x)Ga_(y)Al_(1-x-y)N, 0<=x<=1, 0<=y<=1) light-emittingdevice and manufacturing method thereof.

BACKGROUND TECHNOLOGIES

Indium gallium aluminum nitride (In_(x)Ga_(y)Al_(1-x-y)N, 0<=x<=1,0<=y<=1) is one of the optimal materials for manufacturingshort-wavelength light-emitting devices. Recently, many newlight-emitting devices have been manufactured using InGaAlN materials,such as blue, green, ultraviolet, and white light-emitting diodes(LEDs). The existing technologies indicate that the majority of theInGaAlN light-emitting products are manufactured on sapphire substrates.Currently, these technologies are publicly available. For example,Japanese patent JP2737053 discloses a method for fabricating GaNlight-emitting devices on a sapphire substrate. Because sapphire is aninsulator, it is required that the two electrodes of an InGaAlNlight-emitting device manufactured on a sapphire substrate be positionedon the same side of the chip. As a result, the chip fabrication processis more complex, with increased packaging difficulty. In addition, theproduct yield is reduced. Consequently, the device reliability islessened and the product costs are increased. Furthermore, the thermalconductivity of sapphire is low. If high-power devices are desired, heatdissipation remains an issue. One solution is to use SiC substrate tofabricate GaN materials based on the fact that SiC is electricallyconductive and has a high thermal conductivity. Hence, technically,using SiC substrates can solve the aforementioned problems. U.S. Pat.No. 5,686,738 discloses a method for fabricating InGaAlN light-emittingdevices on SiC substrates. However, SiC substrates are very expensive,which results in high costs if they are used in manufacturing InGaAlNmaterials. Therefore, from a production-cost point of view, SiCsubstrates are not suitable for high-volume production. Another solutionis to fabricate InGaAlN materials on silicon substrates. Since siliconis a well-tested semiconductor material with low costs and high thermalconductivity, and silicon-processing techniques are mature, usingsilicon substrate in manufacturing InGaAlN light-emitting devices cannot only facilitate a vertical-electrode device structure, but alsosignificantly reduces the costs. However, since the band gap of siliconis fairly narrow and silicon exhibits considerable absorption of visiblelight, InGaAlN light-emitting devices directly fabricated on a siliconsubstrate exhibit low luminescence efficiency due to absorption of lightby the substrate. Another solution available in the existingtechnologies is to bond a conductive substrate to the InGaAlN materialfabricated on a sapphire substrate. The sapphire substrate issubsequently removed, and electrodes can then be placed on both sides ofthe substrate. Nevertheless, since sapphire is very hard and resistantto acid or base corrosion, it is very difficult to remove a sapphiresubstrate. Although laser-lift-off technologies can be used to removesapphire substrates, the product yield and manufacturing efficiencyremain low. The laser-lift-off process can also cause certain damage tothe InGaAlN material. Therefore, it is difficult to apply this method tovolume production.

CONTENT OF THE INVENTION

One purpose of the present invention is to provide a type of InGaAlNlight-emitting device. Such devices have vertical electrode structures,which reduces the manufacturing costs and increases the luminanceefficiency. Another purpose of the present invention is to provide amethod for fabricating InGaAlN light-emitting devices with theaforementioned vertical electrode structure. According to this method, alayered InGaAlN semiconductor structure is grown on a silicon substrate.Subsequently, the layered InGaAlN semiconductor structure is bonded toanother conductive substrate. A low-cost manufacturing process is usedto remove the silicon growth substrate and complete the manufacturing ofthe light-emitting device. The method disclosed herein simplifies themanufacturing process and reduces the manufacturing costs.

The structure of a light-emitting device fabricated in accordance withone embodiment of the present invention includes a conductive substratewith a main surface and a back surface. The structure further includes ametal bonding layer on the main surface of the conductive substrate. Inaddition, the structure includes a light-reflection layer on the metalbonding layer. The structure also includes an In_(x)Ga_(y)Al_(1-x-y)N,0<=x<=1, 0<=y<=1 multilayer structure which includes at least a p-typeand an n-type layer on the light-reflection layer. The p-type InGaAlNsemiconductor material has direct contact with the light-reflectionlayer. Furthermore, ohmic contacts are respectively fabricated on theIn_(x)Ga_(y)Al_(1-x-y)N multilayer structure and on the back surface ofthe conductive substrate.

A method for manufacturing a light-emitting device, comprising thefollowing steps:

(a) fabricating an In_(x)Ga_(y)Al_(1-x-y)N (0<=x<=1, 0<=y<=1)semiconductor multilayer structure which includes at least a p-type andan n-type layer on a (111) silicon growth substrate. The multilayerIn_(x)Ga_(y)Al_(1-x-y)N semiconductor material (22-26) includes an AlNbuffer layer (22), an n-type GaN layer (24), a GaN/InGaNmulti-quantum-well layer (25), and a p-type GaN layer (26). Theoutermost layer is p-type layer (26). An undoped GaN layer (23) can beplaced between AlN buffer layer (22) and the n-type GaN layer (24). TheAlN buffer layer can be doped or undoped;

(b) forming a light-reflection layer and a metal bonding layer on theIn_(x)Ga_(y)Al_(1-x-y)N multilayer structure;

(c) bonding the main surface of a conductive substrate with theaforementioned metal bonding layer;

(d) removing the silicon (111) growth substrate, the AlN buffer layerand the undoped GaN layer to expose the n-type InGaAlN layer;

(e) forming a respective ohmic contact on each of the n-type InGaAlNlayer and the back surface of the conductive substrate.

A light-emitting device manufactured in accordance with one embodimentof the present invention has a reliable vertical electrode structure,which simplifies the manufacturing process of the chip, reduces thecomplexity of packaging, increases the product yield and yield, andreduces the manufacturing costs.

The present invention discloses a method for fabricating multilayerIn_(x)Ga_(y)Al_(1-x-y)N semiconductor material on a silicon substrate.Because silicon substrates can facilitate high-quality InGaAlNfabrication, can be easily removed, and are inexpensive, the presentmethod can facilitate large-scale production and lower product costs.

DESCRIPTION OF FIGURES

FIG. 1 is a cross-sectional view depicting a light-emitting device witha vertical electrode configuration in accordance with one embodiment ofthe present invention.

FIG. 2 is a cross-sectional view representing an In_(x)Ga_(y)Al_(1-x-y)Nmultilayer fabricated on a silicon growth substrate, a light-reflectionlayer and a metal bonding layer in accordance with one embodiment of thepresent invention.

FIG. 3 is a cross-sectional view of a metal bonding layer and aconductive substrate in accordance with one embodiment of the presentinvention.

FIG. 4 is a cross-sectional view of a chip obtained by bonding theIn_(x)Ga_(y)Al_(1-x-y)N epitaxial structure as shown in FIG. 2 with themetal bonding layer as shown in FIG. 3 in accordance with one embodimentof the present invention.

FIG. 5 is a cross-sectional view of a light-emitting device obtainedafter removing the growth substrate from the multilayer structure asshown in FIG. 4 in accordance with one embodiment of the presentinvention.

DETAILED EMBODIMENTS

The following sections provide detailed description of the presentinvention in conjunction with the figures and embodiments.

The labels in FIGS. 1 to 5 are defined as follows:

Element 11 is a conductive substrate, element 12 is a metal bondinglayer, element 13 is a light-reflection layer 13, element 14 is aIn_(x)Ga_(y)Al_(1-x-y)N semiconductor multilayer structure, elements 15and 16 are electrodes, element 21 is a silicon substrate, element 22 isan AlN buffer layer, element 23 is an undoped GaN layer, element 24 isan n-type GaN layer, element 25 is a GaN/InGaN multi-quantum-well,element 26 is a p-type GaN layer, element 27 is a light-reflectionlayer, element 28 is a bonding layer, element 31 is a conductive layer,element 32 is an ohmic contact layer, element 33 is a bonding layer 33,and elements C1 and C2 are electrodes.

As illustrated in FIG. 1, in accordance with one embodiment of thepresent invention, the present inventive In_(x)Ga_(y)Al_(1-x-y)Nlight-emitting device includes a conductive substrate 11; above thissubstrate are a bonding metal layer 12 and a light-reflection layer 13.Above said light-reflection layer is an InGaAlN semiconductor multilayerstructure 14. The bottom layer of said InGaAlN multilayer structure is ap-type layer, and the top layer is an n-type layer. The top surface ofthe InGaAlN material is an N-face. Ohmic contacts 15 and 16 arerespectively formed above In_(x)Ga_(y)Al_(1-x-y)N multiplayer structure14 and beneath conductive substrate 11.

The material used for conductive substrate 11 can be any type ofsemiconductor or metal material. Considering electrical and thermalconductivity, manufacturability, and costs, well establishedsemiconductor material, such as silicon, and common metals, such ascopper, stainless steel, silver, and kovar (a nickel-cobalt ferrousalloy). Since In_(x)Ga_(y)Al_(1-x-y)N material bonds poorly withconductive substrate 11, bonding layer 12 is added between substrate 11and InGaAlN structure 14. Bonding layer 12 not only has good bondingcapabilities but also forms a good ohmic contact with conductivesubstrate 11. Furthermore, bonding layer 12 ideally can sustainsubsequent fabrication processes and remain damage-free. Bonding layer12 can be a single layer or a multilayer structure. Since conductivesubstrate 11 exhibits a high carrier density, there is a wide range ofselection for the metal for bonding layer 12 so long as the metal hasgood bonding capabilities and exhibits good reliability. In order tocreate a reliable bonding, a metal used for the bonding layer ideallyhas a low melting point. For example, one can select gold (Au), zinc(Zn), indium (In), tin (Sn), palladium (Pd), and alloys thereof.Considering the effect of diffusion between metal layers on the ohmiccontact and the stability of the metal during fabrication processes, itis preferable to use gold or gold alloys, such as gold-zinc and gold-tinalloys, as the bonding metal.

Since metals such as Ni, Au has poor reflectivity, such metal layersreflect poorly the light produced by InGaAlN multilayer structure 14. Asa result, the light extraction efficiency is lowered. Therefore, one caninsert a light-reflection layer between bonding metal layer 12 andInGaAlN multilayer structure 14. As described above, the bottom layer ofthe present inventive InGaAlN multilayer structure is a p-type layer.Therefore, light-reflection layer 13 ideally forms a good ohmic contactwith a p-type InGaAlN material. In one embodiment of the presentinvention, this light-reflection layer 13 is platinum (Pt), because Ptnot only forms a good ohmic contact with p-type InGaAlN material, butalso exhibits a high reflectivity to visible light. Meanwhile, Pt isalso very stable. To achieve electroluminescence, InGaAlN multilayerstructure 14 contains at least one n-type layer and one p-type layer. Toincrease the luminescence efficiency, typically a double hetero junctionor a multi-quantum-well structure is inserted between the n-type layerand p-type layer. The InGaAlN multilayer structure can also employ anypublicly available structure. The proportion of In, Ga, and Al in theluminescent layer 14 can vary between 0-1, which allows adjustment ofthe device's luminescence wavelength.

An In_(x)Ga_(y)Al_(1-x-y)N light-emitting device 14 manufactured inaccordance with one embodiment of the present invention exhibits anitrogen-atom upper surface, which allows the InGaAlN material to beremoved using chemical etching and avoids the use of Inductively CoupledPlasma (ICP) etching system. Hence, chemical etching can be used tocoarsen the device surface, which can improve the light-extractionefficiency.

The ohmic electrode 15 on InGaAlN multilayer structure 14 can be basedon Au—Ge—Ni alloy or metals with a small work function, such as Ti andAl. In principle, any metal can be used if the doping density issufficiently high. In one embodiment of the present invention, aAu—Ge—Ni alloy is used to form ohmic contact 15, since Au—Ge—Ni alloyexhibits good stability, resistance to corrosion, and resistance tooxidization. In addition, any metal can be used to form ohmic contact 16on the back surface of conductive substrate 16, since this conductivesubstrate is configured with a high carrier density. In one embodimentof the present invention, Au, Ni—Au alloy, and/or Ti—Au alloy can beused for the electrode.

A method for manufacturing a light-emitting device, comprising:

A multilayer In_(x)Ga_(y)Al_(1-x-y)N multilayer structure 22-26 isfabricated on a (111) silicon substrate 21. The fabrication can use anypublicly available deposition process, such as Chemical Vapor Depositionand Molecular Beam Epitaxy. The fabrication process of InGaAlN can bebased on any publicly available approach. In one embodiment of thepresent invention, In_(x)Ga_(y)Al_(1-x-y)N multilayer structure 22-26 isfabricated in the following order: AlN buffer layer 22, undoped GaNlayer 23, silicon-doped GaN (n-type) layer 24, GaN/InGaNmulti-quantum-well layer 25, and magnesium-doped (p-type) layer 26. Thesurface of silicon substrate 21 is engraved with grooves to release thestress created by lattice and thermal mismatch between silicon substrate21 and In_(x)Ga_(y)Al_(1-x-y)N multilayer structure 22-26 and to preventcracks.

Upon completion of the fabrication of multilayer In_(x)Ga_(y)Al_(1-x-y)Nsemiconductor material 22-26, an annealing process is performed toactivate the p-type dopants. A light-reflection layer 27 is built on topof the p-type layer of multilayer In_(x)Ga_(y)Al_(1-x-y)N semiconductormaterial 22-26. At the same time, this light-reflection layer also formsa good ohmic contact to the p-type layer. In one embodiment of thepresent invention, platinum is used for light-reflection layer 27. Toimprove the ohmic-contact properties, this electrode layer needs toundergo an annealing process so it can be alloyed. Abovelight-reflection layer 27 a metal bonding layer 28 is formed. In theory,any metal can be used for bonding layer 28. However, in order to createa reliable bonding, one can use a metal of which the melting point isnot very high. Embodiments of the present invention uselow-melting-point alloys such as Au—Zn, Au—Sn, and Au—In alloy, as wellas pure Au. Bonding layer 28 can be a single-layer or multilayerstructure. Light-reflection layer 27 and metal bonding layer 28 can bestacked together and then be alloyed.

At the same time, an ohmic contact layer 32 can be formed on top of aconductive substrate 31. Depending on the electric conductivity of asilicon substrate, metal materials such as nickel, gold, platinum, andtitanium can be used for forming a single or multilayer ohmic contact32. Subsequently, metal bonding layer 33 is formed on ohmic contactlayer 32. The material-selection criteria for bonding layer 33 aresimilar to those for bonding layer 28. It may not be necessary tofabricate ohmic contact layer 32 and bonding layer 33 if conductivesubstrate 31 is a low-melting-point metal. If this is the case, theohmic-contact layer can by used directly as the bonding layer 33. Metalbonding layer 33 can be constructed using electron beam evaporation,magnetron sputtering or any other metal deposition methods. Bondinglayer 28 is then bonded with conductive substrate 31 after the formationof metal bonding layer 33. In one embodiment of the present invention,the two bonding layers are bonded after being placed under a certainpressure in a given temperature for a predetermined period of time.

After bonding, silicon substrate 21 is removed. Silicon substrate 21 canbe removed by using a technique such as mechanical grinding, dryetching, chemical etching or any combination of the above methods. Inone embodiment of the present invention, the silicon substrate isremoved by chemical etching using a solution based on hydrofluoric acid,nitric acid, and acetic acid.

The InGaAlN material is exposed after silicon substrate 21 is removed.Because AlN buffer layer 22 and undoped GaN layer 23 may impede theformation of good ohmic contact, they are ideally removed in order toexpose n-type layer 24 which has high carrier density and to form anohmic contact on the exposed n-type layer 24. Methods for removing AlNbuffer layer 22 and undoped GaN layer 23 include dry etching techniquessuch as reactive ion etching (RIE) and ICP etching system, as well aswet etching techniques based on concentrated phosphoric acid or alkalietching. Next, an ohmic contact layer C1 is formed on n-type GaN layer24, and an ohmic contact layer C2 is formed on conductive substrate 31.This way, an InGaAlN light-emitting device with a vertical electrodestructure in accordance with one embodiment of the present invention isobtained.

The following three examples further illustrate the method disclosed inthe present invention.

Example 1

Referring to FIG. 2, the fabrication of a light-emitting device startswith preparing a 2-inch silicon (111) substrate 21. Using Chemical VaporDeposition, multilayer In_(x)Ga_(y)Al_(1-x-y)N semiconductor material22-26 is fabricated in the following order: AlN buffer layer 22, undopedGaN layer 23, silicon-doped n-type GaN layer 24, five-period GaN/InGaNmulti-quantum-well layer 25, and magnesium-doped p-type layer 26. Uponcompletion, the wafer is annealed in a nitrogen environment at 700° C.for approximately 30 minutes to activate the Mg dopant. Subsequently, aplatinum layer 27, approximately 50 nanometers thick, and a gold layer28, approximately 1000 nanometers thick, are deposited on the p-typelayer using electron beam evaporation. Referring to FIG. 3, a nickellayer 32, approximately 100 nanometers thick, and a gold layer 33,approximately 1000 nanometers thick, are formed on silicon (111)substrate 31. Subsequent to the deposition, the wafer on which theInGaAlN thin films are epitaxially grown is bonded with the silicon(111) substrate on which nickel and gold has been deposited. Thisbonding process is performed under a pressure of 600 kg at 300° C.,which facilitates a strong bond. A structure as shown in FIG. 4 is thenobtained. The bonded wafers are then placed in a solution that includeshydrofluoric acid, nitric acid, and acetic acid until the silicon growthsubstrate is completely removed. Note that, prior to the chemicaletching, a nickel/gold protection thin film is formed on the backsurface of substrate 31 to protect substrate 31 from being chemicallyetched. After chemical etching, the InGaAlN thin films are exposed. Theoutermost layer is AlN buffer layer 22. AlN buffer layer 22 and undopedGaN layer 23 are then removed by chemical etching based on concentratedphosphoric acid. Next, a layer of gold-germanium-nickel alloy,approximately 100 nanometers thick, is deposited on n-type GaN layer 24.After the deposition process, the structure is placed in a chamber withnitrogen gas at 300° C. for 3 minutes to form an alloy. In addition, alayer of gold, approximately 1000 nanometers thick, is deposited on thelayer of gold-germanium-nickel alloy. Electrode C1 with a diameter ofapproximately 100 microns is then formed by photo lithography. ElectrodeC2 is formed on the back surface of substrate 31 by photo lithography.The wafer is then diced into 1000 micron X 1000 micron chips. After wirebonding and packaging, light-emitting devices as shown in FIG. 5 areobtained.

Example 2

Referring to FIG. 2, the fabrication of a light-emitting device startswith preparing a 2-inch silicon (111) substrate. A number of10-nanometer-deep grooves with a crisscross pattern are created on thesilicon substrate by using photo lithography and ICP etching, therebyforming a number of square-shaped mesas approximately 350 micron X 350micron in size. Using Chemical Vapor Deposition, anIn_(x)Ga_(y)Al_(1-x-y)N multilayer structure is fabricated in thefollowing order: an AlN buffer layer, an undoped GaN layer, asilicon-doped n-type GaN layer, a five-period GaN/InGaNmulti-quantum-well layer, and a magnesium-doped p-type layer. Uponcompletion of the fabrication of these layers, to the wafer is annealedin a nitrogen environment at 700° C. for approximately 20 minutes toactivate the Mg dopant. Subsequently, a platinum layer, approximately100 nanometers thick, a gold layer, approximately 500 nanometers thick,and a gold-zinc alloy layer, approximately 200 nanometers thick, aredeposited on the p-type layer by using electron beam evaporation. Aplatinum layer, approximately 50 nanometers thick, a gold layer,approximately 500 nanometers thick, and a layer of gold-indium alloy,approximately 100 nanometers thick, are fabricated on both sides of aconductive silicon (100) substrate. After the deposition, the wafer onwhich the InGaAlN thin films are epitaxially grown is bonded with thesilicon (100) substrate on which only metal layers are deposited. Thebonding process is performed under a pressure of 800 kg at 260° C.Subsequently, the silicon (111) substrate is removed using ICP etchingto expose the InGaAlN thin films. The outermost layer is the AlN bufferlayer. Next, the AlN buffer layer and the undoped GaN layer arecompletely removed using ICP etching. A titanium layer, approximately 50nanometers thick, and an aluminum layer, approximately 100 nanometersthick, are deposited the n-type GaN layer. After the deposition process,the wafer is then placed in a chamber with nitrogen gas at 500° C. for 3minutes to form an alloy. In addition, a titanium layer, approximately10 nanometers thick, and a gold layer, approximately 1200 nanometersthick, are deposited on the titanium/aluminum electrode. Subsequently,square-shaped electrodes with each side of 100 microns are formed byphoto lithography. Furthermore, the wafer is diced along the pre-formedgrooves, after which individual light-emitting chips can be obtained.After wire-bonding and packaging, light-emitting devices in accordanceto one embodiment of the present invention are obtained.

Example 3

On a 2-inch silicon (111) substrate, using Chemical Vapor Deposition, anIn_(x)Ga_(y)Al_(1-x-y)N multilayer structure is fabricated in thefollowing order: an AlN buffer layer, an undoped GaN layer, asilicon-doped GaN n-type layer, a five-period GaN/InGaNmulti-quantum-well layer, and a magnesium-doped p-type layer. Uponcompletion of the fabrication of these layers, the wafer is annealed ina nitrogen environment at 700° C. for 30 minutes to activate the Mgdopant. Subsequently, a platinum layer, approximately 5 nanometersthick, a nickel layer, approximately 5 nanometers thick, and a goldlayer, approximately 10 nanometers thick, are deposited on the p-typelayer by using electron beam evaporation. After the deposition process,the structure is placed in a chamber with a nitrogen-oxygen mixture gasat 550° C. for 3 minutes to form an alloy. Subsequently, a gold layer,approximately 500 nanometers thick, is deposited on the alloy. Agold-tin alloy, approximately 500 nanometers thick, is formed on apolished copper substrate. The wafer on which the InGaAlN thin films areepitaxitially grown is bonded with the copper substrate on which thegold-tin alloy is deposited under 500 kg of pressure, at 300° C. Next,ICP etching is used to completely remove the silicon substrate, the AlNbuffer layer, and the un-doped GaN layer. A layer ofgold-germanium-nickel alloy, approximately 100 nanometers thick, is thendeposited on the n-type GaN layer. After the deposition process, thestructure is then placed in a chamber with nitrogen gas at 300° C. for 3minutes to form an alloy. In addition, a gold layer, approximately 100nanometers thick, is deposited on the gold-germanium-nickel electrodelayer. After photo lithography, an electrode is formed with a diameterof approximately 80 microns. After the wafer is diced into 200 micron X200 micron chips, wire bonding, and packaging, light-emitting devices inaccordance with one embodiment of the present invention are obtained.

1-9. (canceled)
 10. An In_(x)Ga_(y)Al_(1-x-y)N (0<=x<=1, 0<=y<=1)light-emitting device, the device comprising: a conductive substrateconfigured with a front surface and a back surface; a metal bondinglayer situated on the front surface of the conductive substrate; alight-reflection layer situated on the metal bonding layer; anIn_(x)Ga_(y)Al_(1-x-y)N (0<=x<=1, 0<=y<=1) semiconductor multilayerstructure situated on the light-reflection layer, wherein theIn_(x)Ga_(y)Al_(1-x-y)N multilayer structure comprises at least onep-type layer and one n-type layer, and wherein the p-type layer iscoupled to the light-reflection layer; and two electrodes, wherein oneelectrode is situated on the In_(x)Ga_(y)Al_(1-x-y)N semiconductormultilayer structure, and the other electrode is on the back surface ofthe conductive substrate.
 11. The In_(x)Ga_(y)Al_(1-x-y)N (0<=x<=1,0<=y<=1) light-emitting device of claim 10, wherein the InGaAlNsemiconductor multilayer structure is configured such that the side ofthe InGaAlN semiconductor multilayer structure which is situated closerto the conductive substrate exhibits a Ga-face, and the side of theInGaAlN semiconductor multilayer structure which is situated fartherfrom the conductive substrate exhibits a N-face.
 12. TheIn_(x)Ga_(y)Al_(1-x-y)N (0<=x<=1, 0<=y<=1) light-emitting device ofclaim 10, wherein the light-reflection layer comprises at least aplatinum layer.
 13. The In_(x)Ga_(y)Al_(1-x-y)N (0<=x<=1, 0<=y<=1)light-emitting device of claim 10, wherein the ohmic electrode on theInGaAlN semiconductor multilayer structure comprises agold-germanium-nickel alloy.
 14. The light-emitting device of claim 10,wherein the conductive substrate comprises silicon, copper, or kovar.15. A method for manufacturing a light-emitting device, the methodcomprising: (a) fabricating a an In_(x)Ga_(y)Al_(1-x-y)N (0<=x<=1,0<=y<=1) semiconductor multilayer structure which comprises at least ann-type layer and a p-type layer on a silicon (111) growth substrate;wherein the In_(x)Ga_(y)Al_(1-x-y)N (0<=x<=1, 0<=y<=1) semiconductormultilayer structure includes a AlN buffer layer, an n-type GaN layer, aGaN/InGaN multi-quantum-well layer, a p-type GaN layer; wherein theoutermost layer is the p-type layer; wherein between the AlN bufferlayer and the n-type GaN layer is an undoped GaN layer; and wherein theAlN buffer layer can be doped or undoped; (b) forming first alight-reflection layer and then a metal bonding layer on the surface ofthe In_(x)Ga_(y)Al_(1-x-y)N semiconductor multilayer structure; (c)bonding the main surface of a conductive substrate with the metalbonding layer; (d) removing the silicon (111) growth substrate, AlNbuffer layer, and undoped GaN layer to expose the n-type; and (e)forming electrodes on the n-type layer and the back surface of theconductive substrate, respectively
 16. The method of claim 15, furthercomprising patterning the silicon (111) growth substrate by forminggrooves and mesas thereon prior to fabricating theIn_(x)Ga_(y)Al_(1-x-y)N semiconductor multilayer structure.
 17. Themethod of claim 15, further comprising forming an ohmic contact layerand a metal bonding layer on the main surface of the conductivesubstrate prior to bonding the conductive substrate with the metalbonding layer.
 18. The method of claim 15, wherein the silicon (111)growth substrate is removed using an etching solution comprising nitricacid, hydrofluoric acid, and acetic acid; and wherein removing the AlNbuffer layer and undoped GaN layer comprises using dry etchingtechniques such as reactive ion etching and ICP etching, or wet etchingtechniques using concentrated phosphoric acid or alkali.